1. Field of the Invention
The present invention relates to an imaging apparatus equipped with an image-stabilizing (image shake correction/shake reduction) system.
2. Description of the Related Art
In recent years, mobile electronic devices which are designed mainly for taking still/moving photographic images, such as digital cameras (still-video cameras) and digital camcorders (motion-video cameras), and other mobile electronic devices which are designed to be capable of taking such photographic images as a subsidiary function, such as mobile phones equipped with a camera and smart devices (smart phones or tablet computers, etc.) equipped with a camera, have become widespread, and there has been a demand to miniaturize the imaging units incorporated in these types of mobile electronic devices. In order to miniaturize an imaging unit, it is known in the art to construct an optical system of an imaging unit as a bending optical system which reflects (bends) light rays using a reflection surface of a reflector element such as a prism or a mirror. Using a bending optical system in an imaging unit makes it possible to achieve a reduction in thickness of the imaging unit, especially in the direction of travel of the incident light emanating from an object to be photographed.
In addition, there also has been a tendency for demand to equip imaging units with a so-called image-stabilizing (image shake correction/shake reduction) system that is designed to reduce image shake on the image plane that is caused by vibrations such as hand shake. The following four different types of imaging units are known in the art as imaging units using a bending optical system which are equipped with an image-stabilizing system: a first type (disclosed in Japanese Unexamined Patent Publication Nos. 2009-86319 and 2008-268700) in which an image sensor is moved in directions orthogonal to an optical axis to reduce image shake, a second type (disclosed in Japanese Unexamined Patent Publication No. 2010-128384 and Japanese Patent No. 4,789,655) in which a lens (image-stabilizing lens/image-stabilizing optical element) disposed behind a reflector element (on the image plane side) that has a reflection surface is moved in directions orthogonal to an optical axis to reduce image shake, a third type (disclosed in Japanese Unexamined Patent Publication Nos. 2007-228005, 2010-204341, 2006-330439, and Japanese Patent No. 4,717,529) in which the angle of a reflector element (a reflection surface thereof) and the angle of a lens adjacent to the reflector element are changed to reduce image shake, and a fourth type (disclosed in Japanese Unexamined Patent Publication Nos. 2006-166202 and 2006-259247) in which the entire imaging unit is obliquely moved to reduce image shake.
The applicant of the present invention has proposed an image-stabilizing system which only moves a front lens element(s) of a front lens group along a plane orthogonal to the optical axis of the front lens element(s) to reduce image shake in an imaging apparatus which contains a bending optical system, wherein the front lens group includes a reflector element and the aforementioned front lens element(s) that is positioned on the object side of the reflector element, and the front lens group is disposed on the object side in the entire optical system of the imaging apparatus (disclosed in Japanese Unexamined Patent Publication No. 2013-238848).
In Japanese Unexamined Patent Publication No. H09-251127, in a lens system having a straight optical axis, not a bending optical system, it is disclosed that the first lens element, which is positioned closest to the object side, or the second lens element, which is subsequently positioned behind the first lens element, is rotated (swung) about a rotational center on an optical axis to perform an image-stabilizing operation
Bearing in mind that, in addition to still image photography, moving image photography is now commonly used in imaging apparatuses, there has been a need for further improvement in the image-stabilizing capability in imaging apparatuses. However, movements of an optical element to reduce image shake (image-stabilizing optical element) exert an adverse influence on the optical performance such as aberrations, and a space corresponding to the moving amount of the optical element is required. Accordingly, when attempts are made to improve the image-stabilizing capability, consideration is required to prevent, as much as possible, these conditions (namely, further miniaturization of the image-stabilizing system and minimalization of any reduction in the optical performance due to the image-stabilizing operation) from being impaired.
In the first type of image-stabilizing system, a substrate which is connected to the image sensor moves while following the image sensor; accordingly, the peripheral electrical components, in addition to the image sensor, need to be designed so as to be compatible with such movements, so that the image-stabilizing system tends to be complicated in structure and high in production cost. In addition, although the periphery of the imaging surface of the image sensor needs to have a dust-resistant structure, it is difficult to secure a sufficient space which allows the image sensor to perform an image-stabilizing operation while maintaining a dust-resistant structure within a small imaging unit intended to be incorporated in a cellular phone or a smart device.
In the second type of image-stabilizing system, the moving direction of the image-stabilizing lens during an image-stabilizing operation corresponds to the thickness direction of the imaging unit (the forward/rearward direction with the direction toward an object to be photographed set to correspond to the forward direction), so that a problem occurs with it being difficult to incorporate the image-stabilizing system into the thin imaging unit because the internal space thereof is limited. Conversely, if this type of image-stabilizing system is used, reduction in thickness of the imaging unit becomes limited. A similar problem exists in the type of image-stabilizing system which moves an image sensor, not a lens element, in the thickness direction of the imaging unit.
In the third type of image-stabilizing system, a large space is required to obliquely move the reflector element and the lens adjacent to the reflector element relative to each other, which easily increases the size of the imaging unit. In the fourth type of image-stabilizing system, in which the entire imaging unit is obliquely moved, the increase in size of the image-stabilizing system unavoidable.
In the image-stabilizing system disclosed in Japanese Unexamined Patent Publication No. 2013-238848, the effect of miniaturizing (slimming) the imaging apparatus in a direction along the optical axis of the front lens element is obtained by making the front lens element of the front lens group, which is positioned in front of the reflector element, move in a plane orthogonal to the optical axis of the front lens element. However, in recent years, it has been desired to achieve, up to a high level, both miniaturization and improvement in image-stabilizing performance of the imaging apparatus equipped with an image-stabilizing system.
In the image-stabilizing system disclosed in Japanese Unexamined Patent Publication No. H09-251127, the conceptual rotational centers of the first lens element and the second lens element are set on an optical axis (optical path); however, to achieve this optical configuration, it is required to arrange the rotational supporters for the first lens element and the second lens element at positions deviating from the optical path so as not to cut off light rays traveling in the optical path, which makes it difficult to achieve a small and compact design of the image-stabilizing system.